This invention relates to the recovery of molybdenum from organic mixtures. More particularly, it is concerned with the recovery of molybdenum from spent catalyst mixtures derived from the epoxidation of olefins.
Molybdenum and its compounds are employed as catalysts in wide variety of industrial scale organic reactions. The value of the metal contained in the spent catalyst residues derived from such processes, considered together with the environmental concerns relating to outright disposal of the molybdenum-containing residues, make the recovery of the metal from these residue mixtures an increasingly important consideration.
One important source of such spent catalyst mixtures which contains appreciable amounts of molybdenum, is the process of epoxidizing olefins employing organic hydroperoxides. This process is disclosed in Belgian Pat. No. 647,076 dated June 20, 1966. The spent catalyst residue from this process contains molybdenum compounds together with a complex mixture of organic compounds, notably low molecular weight alcohols derived from the reduction of the hydroperoxide employed in the expoxidation.
This residue, high in organic content, is an attractive potential fuel, but cannot be burned directly without first removing the molybdenum. Metallic oxides in the combustion effluent pose a serious health and pollution problem when such organic spent catalyst residues containing more than about 100 ppm molybdenum are burned.
Because of the foregoing concerns, a number of processes have been suggested for the recovery of molybdenum from spent organic catalyst residues. Most of these methods entail either the use of water-based solvent extraction systems which are not totally effective in recovering the molybdenum, or require expensive or elaborate processing equipment. One shortcoming of simple extraction processes which employ a water-based extractant is the fact that a major portion of the molybdenum contained in organic spent catalyst residues is organically bound and is not water soluble.
The present invention overcomes the problems and disadvantages of the prior art methods for recovering molybdenum from spent catalyst residues by providing a simple, efficient, and economical method.